reference work

The Brockhaus Enzyklopädie, the best-known traditional reference book in German-speaking countries The Lexikon des Mittelalters, a specialised German encyclopedia Encyclopædia Britannica, 15th edition: volumes of the Propedia (green), Micropedia (red), Macropedia (black), and 2-volume Index (blue)

A reference work is a document, such as a paper, book, encyclopedia or periodical (or their electronic equivalents, usually available online), to which one can refer for information. The information is intended to be found quickly when needed. Such works are usually referred to for particular pieces of information, rather than being read in its entirety. The writing style used in these works is informative, with the authors avoiding opinions and the use of the first-person perspective, and emphasizing facts.